Fabrication of Micro-/Submicro-/Nanostructured Polypropylene/Graphene Superhydrophobic Surfaces with Extreme Dynamic Pressure Resistance Assisted by Single Hierarchically Porous Anodic Aluminum Oxide Template

By applying a three-step anodic oxidation method followed by etching and pore widening treatment, etched micro-/submicroscale pits of ∼2 μm and ∼230 nm as well as anodized nanopores of ∼70 nm are combined to form hierarchically porous anodic aluminum oxide (HP-AAO) templates. Hierarchical micro-/submicro-/nanostructured polypropylene/graphene (HMSNS-PP/GP) superhydrophobic surfaces are laminated by a single HP-AAO template, exhibiting the similar arrangement, size, and shape with hierarchical papillae on lotus leaf surfaces. As expected, such a lotus-inspired HMSNS-PP/GP surface has an extremely small roll-off angle of ∼0.5° and a large contact angle of 155.0°, exhibiting high-efficiency self-cleaning characteristics. The HMSNS-PP/GP surface is endowed with static and dynamic wetting stabilities, which are reflected in immersion and impacting tests. After immersion, the HMSNS-PP/GP replica remains fully spotless accompanied with the ability to work under a hydrostatic pressure of ∼3626 Pa for at least 60 min. After impact, the maximum height of bounced droplets is up to 12.4 mm (i.e., 5.3 times the diameter of the droplet) at a Weber number of ∼32.12.